Ultrafiltration refers to a technique for separating (macromolecular) substances or for reconcentrating the same. Ultrafiltration techniques are also used for treating drinking water, for example for removing bacteria and viruses prior to providing drinking water to an end consumer.
Microfiltration and ultrafiltration are distinguished by the degree of separation. If particles are separated having a size of 0.5 μm to 0.1 μm, this is called microfiltration, if the size of the particles is 0.1 μm to 0.01 μm, this is referred to as ultrafiltration.
Known ultrafiltration systems for treating drinking water suffer from a reliability that is partially in need of improvement, in particular when damage of the membrane is involved or when the quality of the water to be filtered varies, e.g. due to weather influences.
The document U.S. Pat. No. 5,476,592 discloses a blood filtration installation. An injection device of the blood filtration installation contains means for checking the integrity of a main filter during blood filtration. These checking means contain a second filter for bacteria retention. Two pressure sensors are connected to the secondary filter. The pressure sensor signals are supplied to a control unit which calculates a differential pressure and compares the same with a threshold value. If a membrane of the main filter is damaged, bacteria might be introduced into the second filter. A resulting clogging leads to an increase of the pressure difference between both sides of the secondary filter. When this differential pressure reaches a threshold value, then the control unit triggers alarm means and causes a stop of the pump.
The document U.S. Pat. No. 6,649,063 B2 discloses a medical therapy system for producing a sterile replacement fluid. A corresponding filter may be tested by means of an integrity test so as to secure that the replacement fluid has been correctly filtered during sterilization.
The document US 2004/0079700 A1 discloses a method of testing the integrity of a membrane. For this purpose, the membrane is supplied with a supply flow of a solution having a known concentration. The downstream (or permeate-sided) concentration of this solution may be detected for determining if there is a defect in the membrane.
The document DE 690 30 992 T2 discloses to make use of a receiving device in dialysis treatments carried out at home, where the uninterrupted presence of a specialist (physician or nurse) for monitoring the sequence of treatment is not intended, which receiving device being connected with a dialysis device, for example, through a telephone line, for performing a monitoring of the dialysis device from a distance and without interruption.